diff --git a/src/bionics.cpp b/src/bionics.cpp
index 43e80c0540a2b..007e0e819de73 100644
--- a/src/bionics.cpp
+++ b/src/bionics.cpp
@@ -845,8 +845,8 @@ bool Character::burn_fuel( int b, bool start )
         return true;
     }
     const bool is_metabolism_powered = bio.is_this_fuel_powered( "metabolism" );
-    const std::vector<itype_id> fuel_available = get_fuel_available( bio.id );
-    const float fuel_efficiency = bio.info().fuel_efficiency;
+    const std::vector<itype_id> &fuel_available = get_fuel_available( bio.id );
+    const float &fuel_efficiency = bio.info().fuel_efficiency;
 
     if( start && fuel_available.empty() ) {
         add_msg_player_or_npc( m_bad, _( "Your %s does not have enought fuel to start." ),
@@ -860,7 +860,7 @@ bool Character::burn_fuel( int b, bool start )
     if( !start ) {
         for( const itype_id &fuel : fuel_available ) {
             const item &tmp_fuel = item( fuel );
-            const int fuel_energy = tmp_fuel.fuel_energy();
+            const int &fuel_energy = tmp_fuel.fuel_energy();
 
             int current_fuel_stock;
             if( is_metabolism_powered ) {
@@ -885,14 +885,14 @@ bool Character::burn_fuel( int b, bool start )
                 if( current_fuel_stock > 0 ) {
 
                     if( is_metabolism_powered ) {
-                        const int kcal_consumed = fuel_energy;
+                        const int &kcal_consumed = fuel_energy;
                         // 1kcal = 4187 J
-                        const units::energy power_gain = kcal_consumed * 4184_J * fuel_efficiency;
+                        const units::energy &power_gain = kcal_consumed * 4184_J * fuel_efficiency;
                         mod_stored_kcal( -kcal_consumed );
                         mod_power_level( power_gain );
                     } else if( tmp_fuel.has_flag( "PERPETUAL" ) ) {
                         if( fuel == itype_id( "sunlight" ) ) {
-                            const double modifier = g->natural_light_level( pos().z ) / default_daylight_level();
+                            const double &modifier = g->natural_light_level( pos().z ) / default_daylight_level();
                             mod_power_level( units::from_kilojoule( fuel_energy ) * modifier * fuel_efficiency );
                         }
                     } else {
@@ -902,16 +902,7 @@ bool Character::burn_fuel( int b, bool start )
                         mod_power_level( units::from_kilojoule( fuel_energy ) * fuel_efficiency );
                     }
 
-                    if( bio.info().exothermic_power_gen ) {
-                        const int heat_prod = fuel_energy * ( 1 - fuel_efficiency );
-                        const int heat_level = std::min( heat_prod / 10, 4 );
-                        const int heat_spread = std::max( heat_prod / 10 - heat_level, 1 );
-                        const emit_id hotness = emit_id( "emit_hot_air" + to_string( heat_level ) + "_cbm" );
-                        g->m.emit_field( pos(), hotness, heat_spread );
-                        for( const auto bp : bio.info().occupied_bodyparts ) {
-                            add_effect( efftype_id( "heating_bionic" ), 2_seconds, bp.first, false, heat_prod );
-                        }
-                    }
+                    heat_emission( b, fuel_energy, fuel_efficiency );
                     g->m.emit_field( pos(), bio.info().power_gen_emission );
                 } else {
 
@@ -940,7 +931,7 @@ bool Character::burn_fuel( int b, bool start )
 
 void Character::passive_power_gen( int b )
 {
-    bionic &bio = ( *my_bionics )[b];
+    const bionic &bio = ( *my_bionics )[b];
     const float &passive_fuel_efficiency = bio.info().passive_fuel_efficiency;
     if( bio.info().fuel_opts.empty() || bio.is_this_fuel_powered( "muscle" ) ||
         passive_fuel_efficiency == 0.0 ) {
@@ -949,29 +940,38 @@ void Character::passive_power_gen( int b )
 
     for( const itype_id &fuel : fuel_available ) {
         const item &tmp_fuel = item( fuel );
-        const int fuel_energy = tmp_fuel.fuel_energy();
+        const int &fuel_energy = tmp_fuel.fuel_energy();
         if( !tmp_fuel.has_flag( "PERPETUAL" ) ) {
             continue;
         }
 
         if( fuel == itype_id( "sunlight" ) ) {
-            const double modifier = g->natural_light_level( pos().z ) / default_daylight_level();
+            const double &modifier = g->natural_light_level( pos().z ) / default_daylight_level();
             mod_power_level( units::from_kilojoule( fuel_energy ) * modifier * passive_fuel_efficiency );
         } else {
             mod_power_level( units::from_kilojoule( fuel_energy ) * passive_fuel_efficiency );
         }
 
-        if( bio.info().exothermic_power_gen ) {
-            const int heat_prod = fuel_energy * ( 1 - passive_fuel_efficiency );
-            const int heat_level = std::min( heat_prod / 10, 4 );
-            const int heat_spread = std::max( heat_prod / 10 - heat_level, 1 );
-            const emit_id hotness = emit_id( "emit_hot_air" + to_string( heat_level ) + "_cbm" );
-            g->m.emit_field( pos(), hotness, heat_spread );
-            for( const auto bp : bio.info().occupied_bodyparts ) {
-                add_effect( efftype_id( "heating_bionic" ), 2_seconds, bp.first, false, heat_prod );
-            }
-        }
+        heat_emission( b, fuel_energy, passive_fuel_efficiency );
         g->m.emit_field( pos(), bio.info().power_gen_emission );
+
+    }
+}
+
+void Character::heat_emission( int b, int fuel_energy, float efficiency )
+{
+    const bionic &bio = ( *my_bionics )[b];
+    if( !bio.info().exothermic_power_gen ) {
+        return;
+    }
+
+    const int &heat_prod = fuel_energy * ( 1 - efficiency );
+    const int &heat_level = std::min( heat_prod / 10, 4 );
+    const int &heat_spread = std::max( heat_prod / 10 - heat_level, 1 );
+    const emit_id hotness = emit_id( "emit_hot_air" + to_string( heat_level ) + "_cbm" );
+    g->m.emit_field( pos(), hotness, heat_spread );
+    for( const auto bp : bio.info().occupied_bodyparts ) {
+        add_effect( efftype_id( "heating_bionic" ), 2_seconds, bp.first, false, heat_prod );
     }
 }
 
diff --git a/src/character.h b/src/character.h
index 8b50c6aa5c8d0..7fd3690490834 100644
--- a/src/character.h
+++ b/src/character.h
@@ -788,6 +788,7 @@ class Character : public Creature, public visitable<Character>
         /**Convert fuel to bionic power*/
         bool burn_fuel( int b, bool start = false );
         void passive_power_gen( int b );
+        void heat_emission( int b, int fuel_energy, float efficiency );
 
         units::energy get_power_level() const;
         units::energy get_max_power_level() const;